Wholly aromatic polyamide

ABSTRACT

Aromatic copolyamides, soluble in organic polyamide solvents, comprise at least 95 mol % of the recurrent structural units of the formulae ##STR1## and up to 5 mol % of structural units containing m-bonds. Here, --Ar--and --Ar&#39;-- are divalent, unsubstituted or substituted aromatic radicals, the valency bonds of which are in the para-position or in a comparable coaxial or parallel position, and --R is a lower alkyl radical.

DESCRIPTION

The invention relates to novel, wholly aromatic polyamides of the dicarboxylic acid/diamine type, which can be spun from their solutions in organic solvents, and to shaped structures produced from them, such as filaments, fibers, fiber pulp, films, sheets and membranes of very high initial modulus (modulus of elasticity), and also to processes for preparing them.

As is known, aromatic polyamides (polyaramides) are raw materials of high thermal and chemical stability and low inflammability. Thus, for example, fibers and films of such raw materials show very good mechanical properties, such as a high strength and high initial modulus (modulus of elasticity), and are very suitable for fields of application in industry--for example for reinforcing plastics or as filter materials.

The preparation of the polymers required for this purpose is best carried out in a known manner by reacting aromatic diamines with aromatic dicarboxylic acid dichlorides in aprotic organic solvents of the amide type (N,N-dimethylacetamide, N-methylpyrrolidone, N,N,N',N'-tetramethylurea and the like)--if necessary in the presence of calcium halides or lithium halides--and neutralizing the hydrogen chloride formed, for example with calcium oxide.

Polyaramides of high strength and high initial modulus are those in which the amide bonds are mutually oriented coaxially or almost parallel, whereby rigid, rod-like polymer molecules are formed.

An example of a typical polyamide of this type is poly(p-phenyleneterephthalamide). Filaments of this material have been described, for example, in German Patent No. 2,219,703.

This polyamide has a number of advantages, but its preparation and its processing are very difficult. Because of the poor solubility in polar organic solvents--and in particular also in the presence of inorganic salts such as calcium chloride or lithium chloride as solubilizers--this polymer already precipitates from the reaction medium shortly after it has been formed. It must be isolated, washed, dried and then redissolved in a spinning solvent. The preferred solvent for preparing the spinning solutions is concentrated sulfuric acid, which causes special problems in handling (occupational safety, corrosion) and waste disposal.

Attempts have therefore been made to avoid these difficulties by developing copolyamides which have good solubility in the known amide solvents and which can also be readily spun and the filaments of which are distinguished, after drawing, by high strength values and initial moduli.

Thus, for example in DE-A-2,144,126, the preparation of soluble aromatic polyamides of high modulus of elasticity was described, according to which substituted 3-(p-aminophenoxy)-4-aminobenzanilides give, with terephthaloyl chloride, readily soluble polyamides which can be spun and drawn to give filaments of good strengths and initial moduli.

The increased solubility is caused here by the metaorientation and the oxygen bridge atom.

In German Patent No. 2,556,883 and in German Offenlegungsschrift No. 3,007,063, copolyamides of terephthalic acid, p-phenylenediamine and 3,4'-diaminodiphenyl ether are described which, in amide solvents, give isotropic solutions which can readily be spun. The filaments are provided with high strengths and moduli by very extensive drawing. A disadvantage in the two abovementioned processes is that the required unsymmetrical diamines can be prepared and purified only by very involved processes.

For this reason, terephthalamides with 3 diamine components in certain defined fractions are described in German Offenlegungsschriften No. 3,510,655 and 3,605,394 or in European patent application No. 0,199,090, respectively, which are readily soluble in amide solvents and, by deformation, give filaments or films of very good strengths and moduli.

Because of the content of non-aromatic chain constituents, such as --O-- or --CH₂ -- groups, the moduli described in the last mentioned publications - up to 68 N/tex is mentioned in German Offenlegungsschrift No. 3,510,655, and up to 79 N/tex in German Offenlegungsschrift No. 3,605,394--are not yet sufficiently high for certain intended applications.

Filaments of the abovementioned poly-(p-phenyleneterephthalamide) described in German Patent No. 2,219,703 reach moduli of up to 99 N/tex only after an expensive thermal aftertreatment (cf. also U.S. Pat. No. 3,767,756, column 11, and German Patent No. 2,219,703, page 14).

The present invention is therefore based on the object of providing aromatic copolyamides of a type which can be converted with the use of amide solvents into shaped structures which are then distinguished by a number of physical properties. In the production of filaments and fibers, in particular high strengths and very high initial moduli should be achievable after appropriate drawing steps. The monomers required for preparing the copolyamides should be readily accessible, and the polymer solutions obtained by the polycondensation should capable of being spun or shaped directly after a filtration process and appropriate degassing.

Novel aromatic copolyamides have now been found which are composed predominantly of para-substituted aromatic chain constituents and, surprisingly, are nevertheless soluble in amide solvents and can be processed from these solutions to give shaped structures such as filaments, fibers, fiber pulp and films or sheets. These copolyamides comprise at least 95 mol %, preferably 100 mol %, of the following recurrent--exclusively rigid--structural units ##STR2## and up to 5 mol % of structural units E and/or F which contain m-bonds and are derived from aromatic dicarboxylic acids (E') and/or from aromatic diamines (F'), the total of the mol fractions of the structural units A+E and the total of the mol fractions of the structural units B+C+D+F being substantially the same.

In these formulae --Ar-- and --Ar'-- are divalent aromatic radicals, the valency bonds of which are in the para-position or in a comparable coaxial or parallel position and which may be substituted by one or two inert radicals such as lower alkyl or halogen, and --R is a lower alkyl radical.

The valency bonds which are in a coaxial or parallel position, point in opposite directions. An example of coaxial bonds pointing in opposite directions are the naphthylene 1,4-bonds. Examples of parallel bonds pointing in opposite directions are, for example, naphthalene 1,5- or 2,6-bonds, whereas the naphthalene 1,8-bonds point in the same direction in parallel.

Divalent aromatic radicals representing --Ar--, in which the valency bonds are in the para-position or in a comparable coaxial or parallel position, are mononuclear or dinuclear fused aromatic radicals such as, for example, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene.

Divalent aromatic radicals representing --Ar'--, in which the valency bonds are in the para-position or a comparable coaxial or parallel position, are mononuclear or dinuclear fused aromatic radicals such as, for example, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene. 1,4-Phenylene is preferred for --Ar-- and --Ar'--.

The radicals --Ar-- and --Ar'-- can be monosubstituted or disubstituted by lower alkyl radicals, i.e. straight-chain or branched alkyl radicals having 1 to 4 carbon atoms, or by halogen, in particular by F, Cl or Br. Preferred alkyl substituents are straight-chain and are, in particular, methyl and ethyl. The preferred halogen substituent is chlorine.

The polyamides according to the invention can contain the unsubstituted radicals --Ar-- and --Ar'-- and the alkyl-and/or halogen-substituted radicals --Ar-- and --Ar'-- side by side in varying proportions.

The polyamide can here contain one type or several types of substituted radicals --Ar-- and --Ar'--; for example, it can contain exclusively methyl-substituted --Ar-- and/or --Ar'-- radicals, or it can contain proportions of --Ar-- and/or --Ar'-- radicals with different alkyl substituents and/or with halogen substituents.

However, the polyamides according to the invention can also contain unsubstituted or substituted radicals --Ar-- and --Ar'-- exclusively. For cost reasons, those polyamides according to the invention are preferred which contain only unsubstituted radicals --Ar-- and --Ar'-- or such radicals substituted up to the extent of about 30 mol %.

Lower alkyl radicals, which can be represented by --R, are likewise straight-chain or branched and have 1-4 carbon atoms. Preferably, --R is a straight-chain radical and especially a radical having 1-2 carbon atoms. Particularly preferably, --R is methyl.

The structural units B, C and D originating from the diamines co-condensed into the polyamide are contained in the aromatic polyamides according to the invention only in the following defined mol percentage ranges, relative to the total quantity of component B, C and D:

structural unit B: 15-25 mol %, preferably 15-20 mol %,

structural unit C: 45-65 mol %, preferably 50-55 mol %,

structural unit D: 15-35 mol %, preferably 25-30 mol %.

These mol % data here relate to the total quantity of the diamine structural units B, C and D.

In addition to the structural units with bonds in the para-position or comparable bonds pointing in opposite directions coaxially or in parallel, the polyamides according to the invention can have up to 5 mol %, relative to all the structural units, of structural units E and F containing m-bonds.

Within the meaning of the present invention, structural units E and F containing m-bonds are those which contain an aromatic nucleus, of which the bonds lying in the chain of the polymer molecule are in the m-position relative to one another.

Examples of such structural units are the radicals of isophthalic acid, m-phenylenediamine, 3,4'-diaminodiphenyl or alkyl- and/or alkoxy-substitution products thereof, or 3,4'- or 3',4-diaminobenzanilide.

It is self-evident to a person skilled in the art that the total of all the structural units (A+E) derived from aromatic acids and the total of all structural units (B+C+D+F) derived from aromatic amines are substantially equal, i.e. that they differ by about 1% as a maximum, preferably by 0.2% as a maximum, and especially that they are equal within the range of the measurements and metering which are possible in practice.

The aromatic polyamides according to the invention are soluble in polar organic aprotic solvents and can be processed directly from these solutions to give shaped structures.

The structures thus obtained are distinguished by a combination of very good technological properties.

In conjunction with the solubility in organic solvents and the economic and ecological advantages resulting therefrom, this processability represents an extremely valuable enrichment of technology in the field of wholly aromatic polyamides.

The outstanding technological properties of the shaped structures according to the invention are based on the incorporation of the amine components B, C and D within the limits indicated above. As can be seen from the comparative experiments described below, the technological properties deteriorate sharply outside the limits indicated.

The cited literature (German Offenlegungsschrift No. 3,510,655) shows that co-terephthalamides obtained from 50% of p-phenylenediamine plus 50% of 3,3'-dimethylbenzidine are sparingly soluble in aramide solvents and cannot be spun (Comparative Experiment 1).

Aromatic polyaramides with one of the single amine components B, C and D are generally known.

Thus, it is known to use terephthalic acid radicals and p-phenylenediamine radicals for polyamides, for example from German Patent No., 2,219,703 cited above. These products are virtually no longer soluble in amide solvents.

The use of benzidines is likewise known. Thus, it is shown in German Offenlegungsschrift No. 3,510,655 cited above, Comparative Example 6, that a terephthalamide of 3,3'-dimethylbenzidine is insoluble in amide solvents and can thus not be spun.

The use of 3,3'-dimethylbenzidine for the preparation of aramides is also cited in the following printed publications:

German Patent No. 3,007,063, page 5, line 25,

Vysokomol. Soed. 12 (1970), No. 10, page 2185,

U.S. Pat. No. 3,318,849,

Belgian Patent No. 569,760,

U.S. Pat. No. 3,671,542 and

U.S. Pat. No. 3,767,756,

P. W. Morgan: "Condensation Polymers", Intersci. Publ. 1965, page 180; Japanese Kokai Tokkyo Koho JP 55/71,751 (80/71,751), abstracted in CA 93 (16), 151120k, and Japanese Kokai JP 50/154,522 (72/154,522), abstracted in CA 84 (16), 106885s.

The use of 4,4'-diaminobenzanilide for the preparation of polyamides has been described in several places

(a) In U.S. Pat. No. 3,671,542, Example 31, it is shown that the polyamide from terephthaloyl choride and 4,4'-diaminobenzanilide is sparingly soluble in amide solvents (in this connection, cf. also U.S. Pat. No. 3,767,756, Example 5). Filaments of this polymer spun from sulfuric acid reach only moderate strengths and moduli.

According to EP-A 218,269, Tables A and B, a diaminobenzanilide-terephthalamide spun from sulfuric acid reaches a high strength and a high modulus only after thermal aftertreatment. In this connection, cf. also EP-A 168,879.

(b) It is also described in U.S. Pat. No. 3,671,542 that a copolyamide from p-phenylenediamine+4,4'-diaminobenzanilide (1:1) and terephthaloyl chloride+dibenzoyl chloride or 2,6-naphthaloyl chloride (1:1) in amide solvents becomes gel-like within a short time. The properties of the filaments (spun from sulfuric acid) are moderate.

Only a 6-component polymer from (p-phenylenediamine+1,5-diaminonaphthalene+4,4'-diaminobenzanilide) and (terephthaloyl chloride+2,6-naphthaloyl dichloride+dibenzoyl chloride) gives a homogeneous solution in amide solvents. The properties of the filaments spun from sulfuric acid are moderate.

(c) According to Preston and collaborators, Polymer letters 4, 1033 (1966), cited also in German Offenlegungsschrift No. 2,144,126, page 1, filaments from 4,4'-diaminobenzanilide-terephthalamide show low strengths and particularly low moduli.

In this connection, also compare:

U.S. Pat. No. 3,354,125, Example 4

J.Polym. Sci. 22, 855 (1969)

J. Appl. Polym. Sci. 16, 3237 (1972), page 3239

J. Macromolek. Sci, Chem. Ed. A7, 325 (1973)

Vysokomol. Soed. Ser. B, 25 (9), 672.

(d) The preparation of diaminobenzanilide-terephthalamide via the Yamazaki reaction (free acid+diamine+pyridine+diphenyl phosphite) gives only low viscosities: Preston and collaborators, J. Polym. Sci; Polym. Chem. Ed. 20, 79 (1982).

(e) In J. Macromolek. Sci. Chem., A7, 325 (1973) and also in Kogyo Kagaku Zassi 1968, 71 (3), 443, copolyamides with 3,4'-diaminobenzanilide are also described.

As can be seen from the cited publications, the respective polyamides are in most cases insoluble in amide solvents, or the filaments spun from organic solvents show only moderate properties.

By contrast, the polyamides of the present invention, which were prepared using mixtures of the amine components B+C+D in defined proportions, surprisingly are soluble in amide solvents and filaments spun from them show a high strength and a very high initial modulus.

The preparation of the aromatic polyamides according to the invention is carried out by solution condensation of aromatic dicarboxylic acid dichlorides with quantities, equivalent thereto, of mixtures of aromatic diamines in known polyamide solvents, i.e. in aprotic, polar solvents of the amide type such as, for example, in N,N-dimethylacetamide, tetramethylurea or especially in N-methyl-2-pyrrolidone. If appropriate, halide salts from the first and second groups of the periodic table can be added to these solvents in a known manner, in order to increase the solvent power or to stabilize the polyamide solutions. Preferred additives are calcium chloride and/or lithium chloride.

This salt addition can be made before the polycondensation or, advantageously, immediatelY after the addition of the acid chloride.

The polycondensation temperatures are usually between -20° C. and +120° C., preferably between +10° C. and +100° C. Particularly good results are obtained at reaction temperatures between +10° C. and +80° C. The polycondensation reactions are preferably carried out in such a way that, after completion of the reaction, 2 to 15 and preferably 5 to 10% by weight of polycondensate are present in the solution. Particularly good results are obtained in concentrations from 5.0 to 7.5% by weight.

In the course of the polycondensation, the molecular weight of the polymer and hence also the viscosity of the reaction batch increase.

A sufficient length of the chain molecule has been reached when the viscosity of the polymer solution obtained in the polycondensation corresponds to an inherent viscosity of the polymer from about 4.5 to 8.0 dl/g.

Inherent viscosity is understood to mean the expression ##EQU1## In this equation, η_(rel) is the relative viscosity, and c is the applied concentration in g/100 ml.

For the purposes of the present invention, it was determined on solutions of in each case 0.5 g of polymer in 100 ml of 98% by weight sulfuric acid at 25° C.

The process, sketched out and known per se, for the preparation of aromatic polyamides is, as far as it is used for preparing the aromatic polyamides according to the invention as described above, likewise a subject cf the invention. This process according to the invention comprises reacting 95 to 100 mol % of acid chlorides of the formula

    Cl--OC--Ar--CO--Cl                                         (A')

and 0 to 5 mol % of aromatic dicarboxylic acid dichlorides (E') containing m-bonds with an equivalent quantity of a diamine mixture composed of 95-100 mol % of a mixture of diamines containing 15-25 mol %, preferably 15-20 mol %, of diamines of the formula

    NH.sub.2 --Ar'--NH.sub.2                                   (B')

45-65 mol %, preferably 50-55 mol %, of diamines of the formula ##STR3## 15-35 mol %, preferably 25-30 mol %, of 4,4'-diaminobenzanilide (D') and of 0 to 5 mol % of aromatic diamines (F') containing m-bonds, in the manner indicated.

Aromatic dicarboxylic acid dichlorides containing m-bonds and aromatic diamines within the meaning of the present invention are those in which the directions of the bonds of the two carboxylic acid chloride groups and of the two amino groups form an angle between one another which corresponds to that of m-bonds. Examples of such dicarboxylic acid dichlorides and diamines, respectively, are isophthalic acid dichloride, m-phenylenediamine, 3,4'-diaminodiphenyl or alkyl- and/or alkoxy-substitution products thereof, or 3,4'- or 3',4-diaminobenzanilide.

In this procedure, the resulting polyamides according to the invention remain dissolved in the solvent.

When the polymer solution has reached the viscosity required for further processing, the polycondensation can be stopped in the usual manner by the addition of monofunctional compounds such as, for example, acetyl chloride. The hydrogen chloride, which has been formed and is loosely bound to the amide solvent, is then neutralized by the addition of basic substances. Lithium hydroxide and calcium hydroxide, but especially calcium oxide, are suitable for this purpose.

For producing shaped structures from the polyamides according to the invention, the resulting neutralized solutions of the polyamides according to the invention are filtered, degassed and further processed in the known manner to give filaments, fibers, fiber pulp, films or also sheets, which are likewise a subject of the invention. This can be carried out, for example, by using a wet-spinning unit, where the polymer solution is extruded through suitable spinnerets into a coagulation bath, the resulting filaments are pulled through washing baths and drawn at a higher temperature. Suitable coagulation baths are aqueous solutions of the same amide solvent which was also used for preparing the polymer. However, aqueous salt solutions such as, for example, calcium chloride solutions can also be used.

When the polymer solutions are extruded and the shaped structures such as filaments or films are taken off out of the coagulation bath, only relatively slight wet drawing of these structures takes place. The structures taken off out of the coagulation baths must therefore be subjected to further drawing after the usual washing and drying, in order to confer on them the desired mechanical properties, such as a high modulus of elasticity and a high tensile strength.

In the production of the filaments and fibers as well as films and sheets according to the invention, the total drawing is thus composed of a slight wet drawing and subsequent more extensive drawing. As a rule, the latter is carried out in the usual manner at an elevated temperature on drawing units, in which single-stage or multi-stage drawing takes place between two godet rolls running at different circumferential speeds.

In order to heat the filaments to the required drawing temperature, contact drawing can be carried out, in which the filaments are pulled over hot plates ("pressing irons") fitted in the drawing region of the drawing unit, which have surface temperatures from 280° C. to 470° C., preferably 360° C. to 460° C. The filaments are thus drawn in a ratio of 1:2.5 up to about 1:12, preferably 1:4 to 1:10.

A likewise suitable variant of the spinning process is the so-called "dry-spinneret/wet-spinning process", as is described, for example, in U.S. Pat. No. 3,414,645. In the latter, spinning takes place from the top downwards and, after leaving the spinneret, the spun filaments first pass through a gaseous medium, preferably air, and then enter an aqueous coagulation bath. The further treatment of the filaments thus produced takes place as described above.

The shaped articles produced from the raw materials according to the invention, such as, for example, fibers, filaments, fiber pulp or films and sheets, are used, for example, as reinforcing materials for plastics or as industrial materials for filtration and insulation. For insulation purposes, it is also possible to apply a polymer solution as a film to the object which is to be insulated and then to remove the solvent and any solubilizers which may be present.

The examples which follow are intended to serve for further clarification of the invention. The proportions of dicarboxylic acid components and diamine components were calculated as 100 mol % in each case.

EXAMPLE 1

Aromatic copolyamide from 100 mol % of terephthaloyl chloride, 50 mol % of 3,3'-dimethylbenzidine, 20 mol % of p-phenylenediamine and 30 mol % of 4,4'-diaminobenzanilide.

254.8 g (1.2 mol) of 3,3'-dimethylbenzidine, 51.9 g (0.48 mol) of p-phenylenediamine, 136.6 g (0.72 mol) of 4,4'-diaminobenzanilide and 78.2 g of anhydrous calcium chloride are dissolved under nitrogen in 14,506 g of N-methylpyrrolidone and reacted between 30.7° C. and 54.2° C. within 36 minutes with 487.2 g of powdered terephthaloyl chloride. The reaction is stopped by addition of a solution of 3.8 g of acetyl chloride in N-methylpyrrolidone, the mixture is stirred for a further 20 minutes at about 60° C. and neutralized with 222 g of a suspension of calcium oxide in N-methylpyrrolidone (65%).

The solution contains 5% of copolyamide and 2.2% of calcium chloride. The inherent viscosity of the copolyamide dissolved is 6.28.

The solution is filtered, degassed and spun by the socalled dry-spinneret/wet-spinning process. For this purpose, it is spun out at a temperature of 100° C. through a spinneret fitted at a distance of 40 mm vertically above a coagulation bath and having 100 orifices of 0.15 mm diameter each into the coagulation bath at a speed of 16 m/min. The coagulation bath is composed of an aqueous 35% solution of N-methylpyrrolidone at a temperature of 60° C.

The spun filaments obtained are taken off through two water baths, through a multi-stage washing machine, over two drying godets at 160° C. and 240° C. and finally over a hotplate at 460° C. at a speed of 70.3 m/min. Here and in the following examples and comparative examples, such a take-off speed was used that a drawing ratio for the filaments of 80% of the maximum drawing ratio resulted. Here and in the following examples, the multifilament yarn is then provided with a protective twist corresponding to α_(m) =30 (DIN 53 832, part 1) and then tested.

In Example 1, the filament denier is 2.55 dtex (DIN 53 830) and the ultimate tenacity together with an ultimate tensile strength elongation of 2.1% is 191 cN/tex (DIN 53 834, part 1).

The initial modulus is 92 N/tex. It is determined from the slope of the tenacity/elongation diagram between 0.3 and 0.5% elongation.

EXAMPLES 2 to 6

Analogously to Example 1, but under the reaction conditions indicated in Table 1 and with the use of the starting materials mentioned there, further aromatic polyamides according to the invention can be prepared.

The polyamides thus obtained, of varying compositions with respect to the diamine structural units B, C and D, can then be spun and drawn directly from the reaction solution, analogously to Example 1.

The spinning and drawing conditions as well as the properties of the filaments thus obtained can also be seen from Table 1.

The following abbreviations are used in Table 1: TPC=terephthaloyl chloride; PPD=p-phenylenediamine; DMB=3,3'-dimethylbenzidine; DABA=4,4'-diaminobenzanilide; NMP=N-methylpyrrolidone; N=wet spinning; TN=dry/wet spinning.

                                      TABLE 1                                      __________________________________________________________________________                 Example                                                                        2    3    4    5    6                                              __________________________________________________________________________     Polymer                                                                        PPD mol     0.52 0.36 0.48 0.66 0.20                                           mol %       20   15   20   25   25                                             g           56.2 38.9 51.9 71.3 21.6                                           DMB mol     1.3  1.2  1.32 1.452                                                                               0.4                                            mol %       50   50   55   55   50                                             g           276.0                                                                               254.8                                                                               280.2                                                                               308.2                                                                               84.9                                           DABA mol    0.78 0.84 0.6  0.396                                                                               0.12                                           mol %       30   35   25   15   15                                             g           177.1                                                                               190.7                                                                               136.35                                                                              90.0 27.3                                           Others      --   --   --   3,4'-                                                                               3,4'-                                                                     DABA DABA                                           mol         --   --   --   0.132                                                                               0.08                                           mol %       --   --   --   5    10                                             g           --   --   --   30.0 18.2                                           LiCl/CaCl.sub.2 g                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                 120.0                                                                               79.6 78.0 84.0 25.6                                           NMP g       12858                                                                               14778                                                                               14472                                                                               15626                                                                               4093                                           TPC g       528.85                                                                              486.2                                                                               487.2                                                                               536.0                                                                                162.4                                         Reaction    30.7-57.5                                                                           31.6-54.7                                                                           29.6-54.7                                                                           31.0-54.4                                                                           14.0-55.0                                      temp. °C.                                                               Reaction    55   37   40   44   50                                             time mins.                                                                     Acetyl      4.1  3.8  3.8  4.2  --                                             chloride g                                                                     CaO.sup.(1) g                                                                              241  222  222  244  74                                             Polymer     6    5    5    5    5.73                                           conc. %                                                                        Salt. conc. %                                                                              2.89 2.17 2.21 2.24 2.56                                                       CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                                                          CaCl.sub.2                                     Polymer     4.86 5.68 6.20 5.47 5.10                                           viscosity                                                                      η.sub.inh                                                                  Spinning and drawing                                                           Process     TN   N    TN   TN   N                                              Spinning    120  120  100  100  100                                            solution                                                                       temp. °C.                                                               Number of   100  100  100  100  100                                            holes in                                                                       spinneret                                                                      Spinneret   0.15 0.10 0.15 0.15 0.15                                           hole diam. mm                                                                  Spinneret/co-                                                                              40   --   40   40                                                  agulation bath                                                                 distance mm                                                                    Coagulation 35   35   35   35   35                                             bath comp.                                                                     % NMP                                                                          Coagulation 80   80   60   60   60                                             bath temp. °C.                                                          Take-off    14   16   16   16.1 16                                             speed m/min                                                                    Drying godet temp. °C.                                                              120  120  120  120  160                                                        160  160  160  160  240                                                        240  240  240  240                                                 Hotplate    405-445                                                                             420-460                                                                             420-430                                                                             390-420                                                                             390-420                                        temp. °C.                                                               Take-off    92.7 44.5 127  150.6                                                                               130.0                                          speed m/min                                                                    Filament properties                                                            Denier dtex 2.05 1.92 1.93 1.81 1.79                                           Tenacity    156  148  190  176  179                                            cN/tex                                                                         Elongation %                                                                               1.9  1.8  2.2  2.2  2.5                                            Initial modulus                                                                            87   87   93   87   80                                             N/tex                                                                          __________________________________________________________________________      .sup.(1) 65% suspension of 96% CaO in NMP                                

COMPARATIVE EXAMPLES 1 to 3

Analogously to Example 1, but under the reaction conditions indicated in Table 2 and with the use of the starting materials mentioned there, further aromatic polyamides according to the invention were prepared.

The polyamides thus obtained, of varying compositions with respect to the diamine structural units B, C and D, were then spun and drawn directly from the reaction solution, analogously to Example 1.

The spinning and drawing conditions as well as the properties of the filaments thus obtained can also be seen from Table 2.

The same abbreviations as in Table 1 are used in Table 2.

                                      TABLE 2                                      __________________________________________________________________________                     Comparative Example                                                            1      2          3                                            __________________________________________________________________________     Polymer                                                                        PPD mol         0.48   0.09       0.72                                         mol %           20     15         30                                           g               51.9   9.7        77.8                                         DMB mol         0.96   0.27       0.96                                         mol %           40     45         40                                           g               203.8  57.3       203.8                                        DABA mol        0.96   0.24       0.72                                         mol %           40     40         30                                           g               217.9  54.5       163.6                                        LiCl/CaCl.sub. g                                                                               CaCl.sub.2 78.5                                                                       LiCl 39.9  CaCl.sub.2 75.7                              NMP g           14576  4125       14035                                        TPC g           488.2  121.8      486.2                                        Reaction temp. °C.                                                                      33.2-57.3                                                                             12.9-61.6  29.4-55.3                                    Reaction time   60     33         49                                           minutes                                                                        Acetyl chloride g                                                                              3.8    --         3.8                                          CaO.sup.(1) g   222    55.5       222                                          Polymer con-    5      4.5        5                                            centration %                                                                   Salt con-       2.2 CaCl.sub.2                                                                        1.5 CaCl.sub.2 + 0.9 LiCl                                                                 2.26 CaCl.sub.                               centration %                                                                   Polymer vis-    4.72   5.18       5.16                                         cosity η.sub.inh                                                           Spinning and drawing                                                           Process         TN     N          TN                                           Temperature of spin-                                                                           90     80         120                                          ning solution °C.                                                       Number of holes in                                                                             100    100        100                                          spinneret                                                                      Spinneret hole  0.15   0.10       0.15                                         diameter mm                                                                    Spinneret/coagula-                                                                             40     --         50                                           tion bath distance mm                                                          Coagulation bath com-                                                                          35     35         35                                           position % NMP                                                                 Coagulation bath                                                                               80     60         60                                           temperature °C.                                                         Take-off speed  16     15.9       16                                           m/min                                                                          Drying godet temperature °C.                                                            120    120        120                                                          160    160        160                                                          240    180        240                                          Hotplate temperature                                                                           420-460                                                                               360-400    410-450                                      °C.                                                                     Take-off speed  40.4   50.4       46.6                                         m/min                                                                          Filament properties                                                            Denier dtex     5.99   2.27       6.31                                         Tenacity cN/tex 100    118        101                                          Elongation %    1.4    1.7        1.5                                          Initial modulus 73     81         73                                           N/tex                                                                          __________________________________________________________________________      .sup.(1) 65% suspension of 96% CaO in NMP                                

The comparative experiments show that, although aromatic polyamides, the compositions of which are outside the ranges according to the invention, can likewise be spun into filaments, the combination of the good mechanical properties of the filaments according to the invention can then not be reached. 

We claim:
 1. An aromatic copolyamide, soluble in organic polyamide solvents, which comprises at least 95 mol % of recurrent structural units of the formulae ##STR4## and up to 5 mol % of structural units E or F or combinations thereof which contain m-bonds and are derived from aromatic dicarboxylic acids (E') or from aromatic diamines (F') or combinations thereof, the totals of the mol fractions of the structural units A+E and of the mol fractions of the structural units B+C+D+F being substantially the same,--Ar-- and --Ar'-- being divalent aromatic radicals other then biphenefene, the valency bonds of which are in the para-position or in a comparable coaxial or parallel position and which are optionally substituted by one or two inert radicals, --R being a lower alkyl radical,and the fractions of the diamine components B, C and D relative to the total quantity of these diamine components being inside the following limits: structural unit B: 15-25 mol % structural unit C: 45-65 mol % structural unit D: 15-35 mol %.
 2. A copolyamide as claimed in claim 1, wherein--Ar-- is 1,4-phenylene, 1,4-, 1,5- or 2,6-naphthylene and --Ar'-- is 1,4-phenylene or 1,4-, 1,5- or 2,6-naphthylene.
 3. A copolyamide as claimed in claim 1, wherein --Ar-- and --Ar'-- are 1,4-phenylene radicals which are unsubstituted or substituted by a lower alkyl radical or by a halogen atom.
 4. A copolyamide as claimed in claim 1, wherein --Ar-- and --Ar'-- are 1,4-phenylene radicals which are unsubstituted or substituted by a methyl group or a chlorine atom.
 5. A copolyamide as claimed in claim 1, wherein --Ar-- and --Ar'-- are unsubstituted 1,4-phenylene radicals.
 6. A copolyamide as claimed in claim 1, wherein --R is a straight-chain alkyl radical having 1 to 2 carbon atoms.
 7. A copolyamide as claimed in claim 1, wherein --R is methyl.
 8. A copolyamide as claimed in claim 1, wherein the structural unit containing m-bonds is the divalent radical of 3,4'- or 3',4-diaminobenzanilide.
 9. A copolyamide as claimed in claim 1, wherein the fractions of the diamine components B, C and D relative to the total quantity of diamine components are inside the following limits:diamine B: 15-20 mol % diamine C: 50-55 mol % diamine D: 25-30 mol %.
 10. A process for preparing an aromatic copolyamide of claim 1, by polycondensation of a dicarboxylic acid chloride with aromatic diamines in a known polyamide solvent, optionally in the presence of an alkali metal halide or alkaline earth metal halide, at an elevated temperature, which comprises reacting 95 to 100 mol % of acid chlorides of the formula

    Cl--OC--Ar--CO--Cl                                         (A')

and 0 to 5 mol % of aromatic dicarboxylic acid dichlorides (E') containing m-bonds with an equivalent quantity of a diamine mixture composed of 95-100 mol % of a mixture of diamines containing 15-25 mol % of diamines of the formula

    NH.sub.2 --Ar'--NH.sub.2                                   (B')

45-65 mol % of diamines of the formula ##STR5## and 15-35 mol % of 4,4'-diaminobenzanilide (D') and of 0 to 5 mol % of diamines (F') containing m-bonds.
 11. The process as claimed in claim 10, wherein a mixture of diamines is reacted which has the following composition:15-20 mol % of B', 50-55 mol % of C', 25-30 mol % of D'.
 12. Shaped structure of the copolyamide of claim
 1. 